It’s the sebum!
The researcher found that mosquitoes that smelled a blend of decanal, which activates the human-specific glomerulus, and 1-hexanol, which activates the human-and-animals glomerulus, would fly upwind in search of the source. “Importantly, they also show that these components are behaviorally relevant to the mosquitoes—mosquitoes will track the binary blend of synthetic odorants in the same way that they respond to whole human odor,” notes Duvall. The decanal and undecanal are probably derived from sebum, an oily substance that—unlike sweat—is secreted from hair follicles regardless of physical activity. Finding a role for sebum in mosquito attraction is novel, Matthew DeGennaro, a researcher in vector-borne diseases at Florida International University who was not involved in the study, writes in an email. “Previously, most the of the focus has been on human sweat components such as lactic acid or on how the human skin microbiome processes sweat and sebum into our distinct odor.”